He was referred to the Channel project in November of that year but it is understood to have had little impact on him.

In March 2015 he was arrested by counter-terrorism police as part of an ongoing investigation and then rearrested the following month when officers uncovered the Australia plot.

He is the second convicted terrorist this year where counter-extremism programmes did not work.

In February, 19-year-old Brusthom Ziamani was found guilty of plotting to behead a British soldier in an echo of the brutal murder of Fusilier Lee Rigby.

Ziamani was arrested in an east London street last August carrying a black flag, a 12in (30cm) knife and a hammer in a rucksack, having earlier researched the location of Army cadet bases in the south east of the capital.

He was only caught by chance when a counter-terrorism officer who knew him became suspicious when he spotted him out of his normal area.

It emerged at his trial that two months earlier he had been placed on the Government’s Prevent programme but had rejected any attempts to confront his rapidly growing Islamist views.

Critics of the Government’s Prevent strategy claim it is ineffective and have called for an overhaul.

The Channel Project was set up following the 7/7 attacks in 2005 and aims to identify people vulnerable to extremism.

It then engages appropriate agencies to address their behaviour and keep them away from danger.

It can include work with schools, social services, police, health and local councils.

Figures in 2013 showed there had been 2,653 referrals since its inception, including 645 aged 12 to 16 and another 113 were aged under 12.

In one case, a three year old child was involved because an entire family was referred.

Previous cases have included a teenage schoolboy in East Lancashire who was referred for regularly drawing bombs and guns.

Another youngster wrote “I want to be a suicide bomber” in a school book.

Others reported were new neighbours behaving oddly, including keeping their curtains shut, a bus passenger expressing racist views and a vulnerable loner who suddenly gained new friends. The police chose to take no further action in those cases.

Of the 2,653 referrals, 67 per cent was associated with Islamist extremism and 14 per cent, or 371 cases, involved far right extremism.

Police and other agencies took further action in 587 cases after assessing the individuals were vulnerable.